Elena, ...for THE five years since I first saw you.

+++Tatiana

Uly, I don't get it - the article is needed in my version and in Tatiana's version it's not needed?
What does the definite article mean here?

Because your sentence is in the present and the present always has an implied NOW as it's temporal adverb. Consequently NOW and FIVE YEARS mean the same thing in your version = THIS WHOLE TIME (definite), which started five years ago.

My translation is also in the present, which is why I changed it around and said "since I first saw you five years ago." Tatiana did the same thing: ...since THE first time I saw you. She also used two separate temporal expressions "for five years" and "since the first time I saw you," which also makes sense.

Unfortunately I don't quite understand ☹

Ok, if you were speaking about the past, you would say "I thought about you for five years" and that would have a beginning and an end - from 1990 to 1996, for example. But in the present, it's harder to express this with a time limit because there IS no limit - saw him five years ago and you're still thinking about him today, tomorrow, the day after tomorrow... So ideally in this situation, you would say "I saw you for the first time five years ago and I've been thinking about you THIS WHOLE TIME or ALL THIS TIME or, in keeping with the definite time frames, THE WHOLE FIVE YEARS or ALL THESE FIVE YEARS.

I got the difference between the past and the present, but Tatiana's version is also in the present and here I don't understand the difference.

Instead of saying “for (the) five years since I first saw you” she broke it up into two separate temporal phrases: for five years (and then explains in a separate clause) since the first time I saw you.

so, the matter is in comma?

In that case, yes.

Ok, then I could have added a comma...
Казнить нельзя помиловать 😀 Thanks.

Yes, you could have - but your new version is more “English”

Good to know 👍